how could i modify a straight cut paper shredder to cut the paper to certain dimensions?
any help would be greatly appreciated

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If they are locked to each other, you'll need to pretty much start from square one making the cutter heads from scratch.
...maybe.
i was just making sure it was do able without exploding it or myself
The old/cheap one that I have still has barbs on the discs, used to munch up credit cards. That means that even if mine were converted to cut strips, those strips would be damaged every 1-2 inches from the barbs. So if you wanted to use 9.5mm strips that were as long as an A4 sheet, they'd all be messed up.
If you can't find a paper shredder to use (which I think may be very hard to find, and even harder to modify), then you could use a guillotine (preferred) or rotary style paper cutter with a guide to force 9.5mm cuts. With a good guide + cutter, you can go very quickly on multiple sheets of paper. I used to cut 1000's of sheets of paper from 8.5 x 11 down to 8.25 square using this method. Could be modified to result in 9.5mm strips, but you'd have to try it out a bit first.
Good luck!
Depending on how your particular shredder is designed and the dimensions required, something like that may work for you.